1. Field of the Disclosure
The present disclosure relates to orthopedic implants, and more particularly, to intramedullary nail assemblies.
2. Description of the Related Art
Intramedullary nails may be used to align and stabilize fractures of a long bone, such as a humerus. In a fractured humerus, an intramedullary nail may be inserted into the intramedullary canal of the humerus and positioned to extend across the fracture line of the humerus. Then, locking screws or other securement devices may be inserted through transverse throughholes formed in the intramedullary nail on opposing sides of the fractured humerus to secure the opposing portions of the fractured humerus together.
To secure the locking screws to in the intramedullary nail, the intramedullary nail may have a cavity accessible from the proximal end of the nail, wherein an insert sleeve is sized and shaped for insertion into the cavity. The insert includes transverse locking holes which are aligned with the transverse throughholes of the nail when the insert sleeve is in the desired position within the cavity of the nail. The transverse locking holes of the insert sleeve have a smaller diameter than the locking screws used to lock the intramedullary nail in a bone. Therefore, the thread of the locking screw cuts into the wall of the insert sleeve, or is firmly received therein, which limits the respective transverse locking hole so that the locking screws are secured against loosening within the transverse locking holes and consequently within the locking holes of the intramedullary nail. Thus, firm fixation of the locking screws in the intramedullary nail can be achieved. As will be contemplated by the skilled person also a tight fit of an unthreaded shank of a locking screw or other transverse locking element will fit said purpose.
Such an intramedullary nail assembly is disclosed in US 2012/0109127 A1. In this document, to secure the insert sleeve within the cavity of the intramedullary nail, the cavity includes an axial stop to prevent the insert sleeve from moving distally therepast and a head space includes an internal thread at the proximal end of the nail for engaging a set screw which prevents the insert sleeve from loosening from the cavity. In addition, in said document, the insert sleeve includes an eccentric nose at the distal end which engages a complementary shaped eccentric portion in the cavity which allows the transverse locking holes in the insert sleeve to be exactly aligned with the transverse throughholes in the proximal end of the intramedullary nail.